Universe Update – January 2014
By Ryan Wyatt
The third Thursday of every month, the Morrison Planetarium hosts “Universe Update” at the 6:30 planetarium show during NightLife. I select my favorite astronomy stories from the past month, and I give a brief run-down of current discoveries while taking audiences on a guided tour of the Universe. As you may or may not know, the planetarium sports a three-dimensional atlas of the Universe, so we can take you places virtually while talking about the latest astronomy news.
I always start at Earth and work my way out to cosmological distances, so I’ll list the news stories in the same order—from closest to farthest from home.
Close to home lies the farthest humans have ever traveled into space—the Moon, which a dozen lucky Americans visited in the late 1960s and early ’70s. Although the last astronauts to visit left more than forty years ago, the Russians landed a remote-controlled rover on the Moon’s surface a few years later. And until last month, that was it: various nations had sent spacecraft into orbit around the Moon, but none had attempted a soft landing. But on December 14th, the China National Space Administration succeeded in landing Chang’e 3 in Mare Imbrium (more poetically, “The Sea of Showers”), which in spite of its name is a smooth, dry, basaltic flow on the Moon’s near side. And last week, the probe awoke from the two-week-long lunar night (originally found the link and images here) to begin its extended science mission. A panorama released by CNSA shows the rover scrawling a loop-de-loop trail on the lunar surface.
(Since the night of the “Universe Update,” the rover seems to have developed problems that may threaten the future success of the mission… Stay tuned.)
Meanwhile, in other rover news, the Mars Opportunity rover just celebrated ten years of exploring the martian surface. In celebration, NASA released “New Findings from Old Rover” describing some of Opportunity’s accomplishments. Not bad for a mission originally spec’ed for 90 days!
Of course, our solar system includes not just planets and their moons, but a host of other objects, including asteroids and comets. Various spacecraft have orbited comets and even soft-landed (i.e., didn’t crash) on the surfaces of asteroids, but no craft has tried to set down on the surface of a comet… And yet comets may hold the secret to understanding more about the origins of our solar system and the source of water on Earth!
Enter Rosetta. Last Monday (Martin Luther King Day here in the United States), the European Space Agency woke up its Rosetta spacecraft after more than two and a half years in hibernation. Launched in 2004, the mission carries three NASA instruments as well as a host of other equipment split between the orbiter and the lander. (The Rosetta mission is named for the Rosetta Stone, which helped linguists decipher hieroglyphics; mission designers hope that the results from the spacecraft will play a similar role in illuminating planetary scientists.) During the decade since its launch, Rosetta has received four gravity assists (three from Earth and one from Mars), observed the collision of NASA’s Deep Impact with Comet Tempel-1, and visited two asteroids (Steins and Lutetia) before going into hibernation for 31 months. Now that it has awakened, Rosetta will maneuver close to Comet 67P/Churyumov-Gerasimenko (call it 67P/C-G for short) in May, and later in the year, Rosetta will release its lander (named “Philae,” after an island in the Nile River where another important archaeological clue to deciphering hieroglyphics was discovered) to touch down gently on the comet’s surface, anchoring itself there with harpoons. And in August 2015, the comet will make its closest approach to the Sun, heating up and releasing the really interesting stuff—water, gas, and dust—that form a cometary tail.
As our travels take us outside the Solar System, I like to point out the vast change in scale between interplanetary distances (eight light hours as measured by the diameter of Pluto’s orbit) and interstellar distances (four light years to the nearest star, Alpha Centauri). As I say this in the planetarium dome, we’re typically just starting to pull away far enough to see the parallax effect as we revolve around the Sun’s location—far, far faster than the speed of light in our virtual spacecraft. But in addition to the stars closest to our own sun, we also see failed stars—brown dwarfs—that we find floating freely between the stars. Not quite stars, not quite planets, brown dwarfs share characteristics of both.
The largest gathering of astronomers in the world took place earlier this month: the winter meeting of the American Astronomical Society (AAS). Brown dwarfs were a big topic of conversation, in particular weather on brown dwarfs! UC San Diego astronomer Adam Burgasser (a former Dean lecturer, BTW) described observations that allowed his team to determine the weather forecast on a brown dwarf 6.5 light years distant. He summarized their findings by singing, “Let it snow (rocks)! Let it snow (sand)! Let it snow (gems)!”
As you might expect, the continuing revelations about extrasolar planets (planets orbiting stars other than the Sun, which we call “exoplanets” for short) also made news at the AAS meeting.
University of Chicago graduate student Laura Kreidberg created a short video to describe her work studying the atmosphere of GJ 1214b, a so-called “super-Earth” with a mysterious atmosphere. Using repeated observations of the planet’s atmosphere with the Hubble Space Telescope, Kreidberg and her team found no evidence for water, carbon dioxide, or methane (the kinds of gases we find in the atmospheres of planets and moons in our solar system). Instead, they hypothesize cloud cover made up of seemingly more exotic stuff—zinc sulfide or potassium chloride, for example.
Speaking of super-Earths, another University of Chicago researcher at the AAS meeting, planetary scientist Nick Cowan, asked whether “Super-Earths Look Like Earth?” I described his research in one of my reports from the AAS meeting, but basically, Cowan is trying to deduce how water-covered Super-Earths might be. Planets covered entirely in water might be less appealing for complex life, so even if it represents a human prejudice, we kinda want our Super-Earths to look a lot like Earth! It implies that there’s more life-friendly real estate in the Universe at large.
In another of my reports from AAS, I described early results from the Gemini Planet Imager, a ground-based instrument that could revolutionize planet detections from the ground, with no space telescope required.
Of course, all the stars we see in the night sky—as well as all the brown dwarfs and exoplanets that astronomers observe—lie within our own galaxy, the Milky Way. But we see other galaxies as well, and two relatively nearby galaxies made it into the news in the past month.
Most recently, University College London announced that a group of undergraduates discovered a supernova in the galaxy M82. Bad weather and total serendipity resulted in them imaging the popular and photogenic galaxy. It just so happened that a supernova had just gone off—and as luck would have it, a Type Ia supernova! That comes as great news to astronomers, because M82 is relatively nearby (a mere 10 million light years away), and Type Ia supernovae provide a critical rung in the cosmic distance ladder.
Also, the recently-released Hubble mosaic of the spiral galaxy M83 will provide data for citizen scientists to mine! Hubble’s Star Date: M83 collaboration with Zooniverse allows you to explore the high-resolution image in search of star clusters of various ages, tagging them in a way that helps astronomers make sense of the data. I blogged about this for our Science Today site a few weeks ago, but at that point, the site had not gone live. Now you can go online and help astronomers chart the star formation history of this gorgeous galaxy.
The Hubble Space Telescope team also released a deep and detailed image of the galaxy cluster Abell 2744, the first image from the Hubble’s Frontier Fields observing program. Because massive galaxy clusters create gravitational lenses that warp, magnify, and focus the light from more distant galaxies, we can see the history of the Universe played out in these “Frontier Fields” images.
All these clumps and clusters of galaxies hints at an underlying framework of dark matter, mysterious stuff that dominated the formation of structure in the early history of the Universe. We can’t see dark matter: we only observe its effects (such as the gravitational lensing in Abell 2744), and sometimes, we get a glimpse at the larger structures formed by dark matter. In one such case, a very bright, very distant quasar has illuminated a vast regions of space around it, shining light on nearby material, observed for the first time by the powerful telescopes at Keck Observatory. The illuminated material shows a filamentary structure that suggests the presence of dark matter strands along which the luminous material flows toward the quasar.
That’s all for now. Check back for next month’s update! Or come to NightLife on Thursday, February 20th, and check out “Universe Update” live in the Morrison Planetarium.
Ryan Wyatt is the director of Morrison Planetarium and Science Visualization at the California Academy of Sciences.
Image: UCL/University of London Observatory/Steve Fossey/Ben Cooke/Guy Pollack/Matthew Wilde/Thomas Wright